I'm going to boil my wort directly in the glass flask, then ice bath it, then pitch the yeast. It's my first starter, i guess i'm doing 1/2 cup DME to 1 pint water or whatever the How To Brew book says.

The question I have is whether or not doing this for ~10 min will sanitize the flask, or whether I should sanitize it first.

I think glass is an insulator, so maybe not all of the flask will heat up? But then the rising steam from the wort through the top of the flask should heat up the sides... who knows. Or I could just sanitize it first anyway and be done with it.

Hmmm... also, I was just realizing that in labs you usually hold a flask above a flame with a stand, or put it on top of some sort of mesh flame guard. I was just planning on putting it directly on the gas stove, so the flames would likely directly touch the glass. Any worries there?

Like others have said, I boil in an erlenmeyer directly on the gas flame and this is how I santize. It is also how I sanitize the foil on the top. I use fermcap-s to control the boil, as it gets really crazy. Even with fermcap, I almost had it erupt on me today, had to spray down with a water bottle. Then I figured out lower temp boil is fine and no foam with the fermcap.